JPH0336577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion apparatus, and particularly to a coal crusher suitable for shortening the startup time of a coal crusher.

BACKGROUND ART Conventionally, in boiler devices and the like that use pulverized coal, various coal pulverizers having the following performance have been used. In other words, (1) Finely pulverizing the raw coal to increase its surface area and increase combustion efficiency.

(2) Dry the crushed pulverized coal inside the crusher.

(3) Separate the pulverized particle size to below the required particle size.

FIG. 1 is a typical example, and shows a schematic diagram of a vertical ring ball mill that uses a low-speed abrasion effect.

First, to explain the structure and operation of the above conventional example, solid line arrows in the figure indicate the flow of coal, and broken line arrows indicate the flow of hot air.Coal is conveyed from the coal feed pipe 1 to the pulverizer, and the coal is sent to the grinding ball 7 side by centrifugal force by the lower grinding wheel 4 which is rotated through the grinder drive motor 2 and reducer 3 in the grinder. A plurality of the crushing balls 7 are arranged in the crusher, and the coal introduced is crushed by the compressive force between the crushing balls 7 and the upper and lower crushing wheels 5, 4. The upper crushing wheel 5 is equipped with an upper crushing wheel pressurizing device 6 in order to improve coal crushing ability and prevent the crushing balls 7 from detaching to the outside.
It is pressurized by In addition, in order to dry the crushed coal internally and transport it, the crusher is equipped with ventilation at the crushing inlet so that hot air 12 and cold air 11 can be mixed appropriately according to the condition of the coal. Piping is provided and a primary fan 13 supplies the ventilation system with the required pressure and amount of air. The amount of hot air and its temperature are controlled to a predetermined amount and temperature based on the state of the coal, ie, the type of coal, humidity, and amount of coal. The hot air is
The pulverized coal enters the pulverizer through the slit-shaped throat gap of the throat ring 8 and is pulverized by the pulverizing balls 7, blowing it up at high speed and transporting it while drying it. Given this, the smaller particles pass through the pulverized coal pipe 16 and are sent to the pulverized coal bin or coal burner 19 of the combustion device, while the coarser particles fall along the side wall of the classifier 9.
It is arranged to circulate back into the crusher. Foreign matter that cannot be crushed, such as stones and pieces of iron, which are mixed with the coal and transferred into the crusher, can be easily taken out and collected in a pyrite box even during operation.

As described above, the pulverizer has a structure suitable for pulverizing the material to be pulverized to a required particle size, drying, and transporting the pulverized material inside the pulverizer.

In recent years, there has been an increasing need for commercial boilers to have so-called medium-load large-capacity boilers, which have a large number of startups and stops and a wide range of load fluctuations, and there has been a strong tendency to rely on coal-fired power generation, especially due to fuel conditions.

On the other hand, in the conventional technology, one of the factors that prevents a rapid load increase is the problem of mill warming time. i.e. the crusher has 10
For about 30 minutes, a predetermined amount of air (generally about 70% of the standard air amount) is introduced into the coal crusher as primary air to perform mill warming, and when the mill outlet temperature reaches, for example, 90 to 100℃, For the first time, a method was adopted in which the mill was started and raw coal was fed from a coal feeder.

Therefore, if it is possible to predict an increase in the number of mills in operation due to an increase in load such as when starting a boiler, it is possible to shorten the mill startup time to some extent by performing this mill warming operation in advance. When increasing the boiler load and increasing the number of mills in operation during normal operation, this mill warming operation must first be performed before turning on the mills, which makes it impossible to cope with rapid load increases. Therefore, in order to start the mill early, it is desirable to keep the mill in a warmed state at all times during boiler operation, that is, to perform constant warming. This is done by injecting primary air into the pulverized coal pipe 16, and the warming air volume is approximately equal to the standard air volume of the mill in order to ensure the minimum speed (the speed necessary to prevent backfire from the furnace) in the pulverized coal pipe 16. Since it is kept at 70%, it produces a larger amount of fuel than a coal burner with no fuel at all.
Next, air is blown into the furnace, and due to the increase in excess air throughout the furnace, fluctuations in the drum level,
The above-mentioned conventional technology has a drawback in that the mill cannot be constantly warmed because this leads to fluctuations in the balance of heat absorption in the furnace and deterioration of thermal efficiency in a low load range. In addition, 14 is a crusher inlet damper, 15 is a mill housing, and 17
indicates an air preheater.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to enable constant warming of a mill with a small amount of primary air without having to carry out long-time mill warming with a large amount of primary air before starting the mill. An object of the present invention is to provide a coal crushing device that can shorten the start-up time of a mill.

In short, the present invention provides a continuous warming pipe having a smaller opening area than the total opening area of the pulverized coal pipes at the mill outlet of a conventional coal pulverizer.

The present invention will be explained below based on the drawings. FIG. 2 is a schematic diagram of an embodiment of the present invention. Note that the same or equivalent parts as in FIG. 1 are given the same reference numerals.

First, the configuration will be explained. FIG. 2 shows a case where one conduit 20 for constant warming of the mill is provided in addition to the pulverized coal pipe 16 at the mill outlet. In this embodiment, the conduit 20 for constant warming is provided during mill operation.
A shutoff valve 21 for closing the coal burner 1 is also provided at the outlet of the above-mentioned constant warming pipe 20.
9 is connected.

Next, the effect will be explained. The cross-sectional area of the constant warming conduit 20 is selected to be sufficiently small compared to the total cross-sectional area of the pulverized coal pipe 16, so the amount of warming air by primary air is such that the minimum speed of the constant warming conduit 20 is ensured. A small amount is sufficient for this purpose, and therefore, it is possible to prevent a large amount of primary air from flowing into the furnace during warming, making it possible to carry out warming at all times. The amount of constant warming air is appropriately selected based on the mill's warming effect (the amount of air must be at least more than the amount of heat dissipated by the mill), and the temperature of the warming air is adjusted so that the temperature of the pipe line at the exit of the mill is at a predetermined value. be controlled. In addition, there is a concern that the above-mentioned warming operation may take too much time when starting up a boiler for the first time to warm a mill that has not been warmed at all. This can be achieved by performing mill warming and then switching to the constant warming operation according to the present invention.

In the above embodiment, the constant warming pipe 2
0 is set to one, but the number of continuous warming pipes 20 is not limited to this, and the number of continuous warming pipes 20 is set to be plural in consideration of uniform warming of the mill, and the outlet thereof is also set to an appropriate number other than the coal burner 19. There is no problem even if it is connected to a certain place.

As explained above, according to the present invention, it is possible to always maintain a mill that is stopped during boiler operation in a warmed-up state, so that the start-up time of the mill can be shortened.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a coal pulverizer according to the prior art, and FIG. 2 is a schematic diagram of an embodiment of the present invention. Explanation of symbols, 1... Coal feed pipe, 4... Lower crushing wheel, 5... Upper crushing wheel, 7... Grinding ball, 9...
...Classifier, 11...Cold air, 12...Hot air, 1
5... Mill housing, 16... Pulverized coal pipe, 18
... Mill outlet damper, 19 ... Coal burner, 20
... Continuous warming conduit.

Claims (1)

[Claims] 1. In a coal pulverizer equipped with means for simultaneously pulverizing and drying raw coal by introducing hot air and transporting the pulverized coal to the burner section of a furnace through a pulverized coal pipe, the outlet section of the coal pulverizer and A coal crushing device characterized in that a conduit for constant warming of the coal crusher is provided between the burner section of the furnace and the pulverized coal tube.